Installations, also called systems or apparatuses below, are known, which have a first vibration-isolated device, also called first sub-system below, and a second sub-system, which can have a similar vibration-isolated setup. The first sub-system can contain a lithography device, while the second sub-system has, for example, a robotic system for loading the lithography device with wafers.
An apparatus for distance measurement in a traffic area is described in the conference abstract “Keeping the appropriate Distance Sensor controlled” (URL: http://www.contitevesna.com/word/press/Kits/Frankfurt/). This publication relates to systems for distance measurement in automobiles (Adaptive Cruise Control=ACC). In the described systems, the distance between two automobiles is measured by means of radar or infrared. If the system determines that the distance to the leading vehicle has fallen below a certain minimum distance, then the velocity of the trailing vehicle is automatically reduced until a minimum distance that can be set within certain limits is achieved again. If the street becomes clear again, then the velocity is accelerated until reaching the desired velocity.
In contrast to the invention, automobiles do not represent a part of the equipment.
A lithography device with an illumination device with a step-by-step operation is loaded by means of a robotic system (U.S. Pat. No. 4,627,010). For reducing the idle time, the relative positions of the mask and wafer is measured, a distance value representing a change in the range measurements is calculated, and the calculated value is compared with a critical value. The latter relates to the attenuation of the vibrations caused by the step-by-step movements of the illumination apparatus.
En general, the sub-systems are not directly connected to each other mechanically, but instead stand in a mutual exchange. This exchange can be, for example, a material exchange, a material transfer, or likewise the insertion of a sub-system or a component of the sub-system, for example, a robotic arm, into the other sub-system. The loading of a lithography device with wafers is also viewed as material exchange.
At least one sub-system here has a vibration-isolated setup. For example, the first sub-system is connected to a reference system via a soft spring-damper element, in order to isolate it against structure-borne vibrations. The second sub-system can also be vibration-isolated, for example, attached to the same reference system via a spring-damper element with increased stiffness. Internal/external forces and/or mass displacements acting on the vibration-isolated sub-systems in one sub-system can lead to a noticeable shift in relative positions.
To be able to guarantee error-free or ordinary operation of the installation, it is necessary to maintain the positions of both sub-systems relative to each other in a defined way with sufficient accuracy. Thus, risks should be prevented both for the sub-systems and their components and also for the exchanged material, for example, during its processing by the lithography device.
Maintaining the necessary relative positions of the sub-systems, which allows error-free operation, can be achieved with active, i.e., regulated vibration-isolated sub-systems. For this purpose, the relative positions are monitored during the operation and held within a predetermined tolerance range. This method is cost-intensive, because this measure requires complicated and thus expensive control mechanisms and maintenance work.
According to an alternative or supplemental method, the relative positions is checked once before commissioning of the installation and set to a predetermined desired value. During operation there is no monitoring and no positional control of the sub-systems. Instead, confidence is placed in the fact that the relative positions of the passively vibration-isolated sub-systems no longer changes significantly. A sub-system is passively vibration-isolated when its position is not regulated.
In such installations, relative movements of the vibration-isolated sub-systems can be limited mechanically, for example, by end stops that define the absolute movement clearance, or by time-limited coupling and/or fixing mechanisms.
The action of the movement limitation, however, can affect the sub-systems contrary to the vibration isolation and does not necessarily provide ordinary operation of the installation.
In these installations, there is no inspection of the relative position of the sub-systems during the operation for simultaneously optimized vibration isolation. That is, it cannot be determined whether the desired position of the two sub-systems is maintained relative to each other and thus whether an error-free or nearly error-free operation takes place. Error functions before and during operation, such as, for example, the transport of a wafer from one sub-system to another and the processing of the wafer by means of the lithography device, cannot be ruled out or prevented.